Electrical shielding and locking means for thermionic tubes



Aug. 3', 1943. K. L. HENDERSON 2,325,770

ELECTRICAL SHIELDING AND LOCKING MEANS FOR THERMIONIC TUBES Filed Feb.18, 1943 20 INVENTOR.

KENNETH L.HENDERSON 7 FIG. 2

lNSULATION Patented Aug. 3, 1943 ELECTRICAL SHIELDING AND LOCKING MEANSFOR THERMIONIC TUBES Kenneth L. Henderson, Irondequoit, N. Y., assignorto Stromberg-Carlson Telephone Manufacturing Company, Rochester, N. Y.,a corporation of New York Application February 18, 1943, Serial No.476,360

2 Claims.

This invention relates to electrical shields and more particularly toshields for thermionic tubes.

In signalling devices utilizing thermionic tubes and especially thosedevices intended to operate at ultra-high frequencies While subjected torough usage or severe vibration, the thermionic tubes thereof must beadequately shielded and must also be securely retained againstaccidental displacement from their respective sockets. Such tubes, whilein use, generate considerable heat and consequently there should be aminimum coverage of the radiating surfaces thereof by any shields used.

In accordance with the main feature of the present invention, there isprovided means for electrically shielding a thermionic tube and forretaining said tube in a tube socket of a device in which it is used.

For a clearer understanding of the invention, reference is made to thedrawing in which Fig. l is an exploded view of a portion of a support,as well as a tube socket and a thermionic tube together with tubeshielding and locking means; Fig. 2 is a fragmentary elevational view ofan assembly of the parts illustrated in Fig. 1; Fig. 3 is a plan view ofthe metal ring which forms a part of the shield; and Fig. 4 is a planview of the socket plate and a fragment of the support to which it isattached.

In the drawing. the numeral 5 designates a sheet-metal support which maybe the chassis of a signalling device. This support has an openingtherein which is shown as covered by a socket plate 6, secured to thesupport. The socket plate is provided with an opening 6a in which a tubesocket l is mounted with its contactors 8 extending downward. While thesocket can be attached to the support in any convenient manner, it ispreferred to provide the upper portion of the socket with a peripheralshoulder 9 of larger size than the opening in the support while thelower portion of the socket is of a size to pass through the mentionedopening. The intermediate portion of the socket is formed with acircumferential groove therein near said shoulder, the groove beingadapted to receive a split locking ring I2 of undulating form. It willbe understood that in assembling the socket on the support, the lowerportion of the socket is inserted in the opening in the support.Thereupon, the split ring is sprung into the groove where it bearsagainst the lower surface of the support to lock the socket in position,with its shoulder 9 firmly engagingthe uppersurface of I the support.

7 The top portion of the socket l is provided with openings adapted toreceive the well-known contactors or plug terminals 13 of a thermionictube into engagement with the socket contact'ors 8. This tube comprisesametal envelope l4 in the form of an inverted cup having an outwardlyoffset rim portion 16 with a shoulder ll. This rim portion of theenvelope is closed by a relatively thick disc of insulating material itin which the mentioned tube contactors i3 are mounted.

Inasmuch as the metal of the tube envelope l4 and the metal of thesupport 5, together with the socket contactors 8, are separated bydielectric such as the insulating base i8 of the thermionic tube and thesurrounding air, the internal elements of the tube and the internalleads connecting the socket contactors 8 thereto are not completelysurrounded by metal. Consequently, the internal portions or" the tubeare only incompletely shielded from external electric and magneticfields and conversely, externally located electrical circuits are onlyincompletely shielded from electric and magnetic fields existing withinthe tube. This electrical leakage results in very objectionable effects,especially at ultra high frequencies.

In order to obviate this leakage, there is provided in accordance withthis invention, novel shielding means which also serves to lock thethermionic tube in its socket. This means includes a metal ring l9secured to the upper surface of the support in a position to encirclesaid socket l, the ring being slightly larger in diameter than thediameter or the offset rim portion 16 of the tube envelope hi and itsbase. The ring at its lower edge is provided with an inwardly extendingannular flange 2'21 of a size to lie between the upper surface of saidsocket plate and the under surface of the shoulder on the socket so thatthe ring is detachably held in position on the support along with thesocket. The annular flange 20 of the ring is provided with a lug 2! toengage a portion of the socket so that the ring is held againstrotation.

The shielding and locking means also includes an annular member 22having an inwardly offset portion provided with a shoulder 23 andgenerally conforming to the shape of the outwardly offset portion l6 ofthe tube envelope M. It will be noted that the member 22 extends onlyfor a limited distance beyond the shoulder ll of the tube envelope, sothat the upper or radiating surengages the projecting portion of thering Hl'in which position these parts are retained by inter- .engagementthereof such as by screw threads formed in these parts. During use,'tneannular member '22 is screwed on to the ring l9 until the Ulm shoulder23 on the memberlby contacting the 7 shoulder I? on the tube, forces thetube against" the socket. c

from the metal tube envelope l4 to the metalsup-V. port 5 so that thepossibility [of electricalleakag'e 1 is reduced to a negligible, amount.time, the tube is locked in its socket and yet the At the same majorportion of the radiating surface of the socket and said socketcontactors'of a metal ring secured at one or its edges in contactingrelation with said support to project from a position on 7 said supportwhere it encircles the base of said tube mounted in said socket, and anannular metal member having an inwardly-offset portion 12 J V a I2,325,770 51;;

conforming to the offset rim portion of said envelope, said member beingprovided with means interlocking it in'telescopic relation with saidring and. with said tube rim portion firmly engaged by said inwardlyofisetportion of said member whereby said tube is retained in saidsocket and whereby electrical leakage at the juncture of said tube basewith said support, is obviated.

--2. The combinationwith a metal support having thereon a socketprovided with contactors and f-a thermionictube of the type comprising acup- By this construction, shielding-parts extend' sl lapedmetalenvelope provided'with an outtwardly extending Shoulder adjacent its'rim as well as a base joined to said rim, said base inreluding-insulating material with contactors mounted thereon to engage saidsocket and said socket contactors, of a metal ring secured at one of itsedges in contacting relation with said support .to project'from aposition on said support where it'encircles the base of the tube mountedin said socket, and an annular metal member conforming tot-he rimportion of'said envelope engaging screw threads for adjusting said mern{beruntil the" shoulder onthe'ring firmly engages the shoulder said'envelope whereby-said tube is-retained in 'sa-id sooket and wherebyelectrical leakage at the juncture'ei said tube base with said support,is'obvi'ated.

' KENNETH L. HENDERSON.-

